The invention relates to a surgical instrument for minimally invasive surgical operations comprising a tool coupled to a drive element at a so-called distal end of a shaft. Such instruments are frequently used as so-called shavers.
Surgical instruments of this type have a proximal and also a distal end section together with a central section extending therebetween. An elongated hollow outer shaft, a frequently hollow, cylindrical drive element which is rotatably mounted in the outer shaft and also a cutting, abrading or milling tool which is arranged at the distal end section of the instrument and coupled to the drive element form the essential components of these instruments.
Besides instruments of a linear nature, surgical instruments are also known wherein the distal end region is bent or cranked in order to enable the surgical instrument to reach less easily accessible working positions and generally, to enlarge the working area of the instrument.
In this connection, it is known to provide the drive element with a flexible section between the proximal and distal end section, wherein said flexible section comprises a plurality of ring segments each of which has a first and a second end region in the axial direction, wherein the first end region comprises two or more projections protruding in the axial direction and the second end region has two or more recesses for accommodating the projections and the ring segments intermesh by way of the projections and recesses in articulated manner.
Surgical instruments of this type are known from EP 0 677 276 B1 for example, wherein the flexible section permits the torque to be effectively transmitted from the proximal end section of the drive element to the distal end section and thus to the tool which is attached there.
Since the shaver typically serves for the removal of body tissue, the channel through the interior of the shaft and the (hollow cylindrical) drive element is used for sucking out the removed bits of tissue.
A disadvantage of these known instruments is that the manufacturing process, and particularly the assembly of the flexible section is a complex matter because the flexible section is only loosely composed of a plurality of ring segments so that, not just during the manufacturing process, but also when disassembling the drive element and withdrawing it from the hollow cylindrical outer shaft, ring segments can get lost, especially too in the operating room.
Another shaver which follows this principle for the construction of the drive element utilising loosely intermeshed ring segments in the flexible section is known from DE 10 2004 046 539 A1.
Another starting point was chosen in EP 0 986 989 B1, wherein the flexible section is formed by a hollow cylindrical element in which the wall thereof is slit in helical manner in the radial direction, whereby alternating teeth and indentations alternate in meandering manner along the helical line and intermesh so that the turns then hold together in the axial direction.
A disadvantage of this solution is that it is considerably less flexible and that fatigue fractures frequently occur due to the alternating bending stresses arising when the shaft is rotating. It would of course be possible to use a reciprocating drive with this instrument, but this can be driven at high rotational speeds in one direction of rotation only.
The object of the invention is to develop a surgical instrument of the type described hereinabove in such a way as to make it more reliable especially when operating at high rotational speeds whilst minimising the expenditure on the manufacturing process. A further aspect lies in the provision of an instrument which is employable in a multiplicity of different work situations.